Electronic protective system



Nov. 11, 1958 1. HOROWITZ 2,860,283

ELECTRONIC PROTECTIVE SYSTEM Filed March 7, 1956 HOR/ZON7I4L l6 47 79 DEFL 5c r/o/v v04 74 GE VERTICAL DEFLEC T/O/V VOLTAGE INVENTOR. IRVING HOROWITZ BY W A TTORNEVS United States Patent 2,860,283 Patented Nov. 11, 1958 2,860,283 ELECTRONIC PROTECTIV E SYSTEM Irving Horowitz, Eatontown, N. 1., assignor, by mesne assignments, of one-half to Isaac S. Blonder and onehalt' to Ben H. Tongue The present invention relates to electronic protective systems and, more particularly, to systems that prevent the destruction of electronic apparatus of the cathoderay type.

Various proposals have been the mosaic of cathode-ray light-sensitive pick-up tubes, such as television cameras and the like, and the fluorescent screens of cathode-ray display tubes, such as those used in oscillography and in television receiving and monitoring systems. In such electronic tubes, an electron stream is directed toward the mosaic or fluorecsent screen and the electron stream is caused periodically to scan across the screen so that it may trace out a predetermined scanning pattern. In television and similar applications, this scanning pattern assumes the form of successive horizontal scans, each vertically displaced one below the other to complete a vertical frame of horizontal scans. Such two-dimensional scanning is effected under the control of horizontal and vertical deflecting means. Loss of the defiection voltages to be supplied to the horizontal and vertical deflection means, or failure in the deflection means themselves, would result in the repetitive impingement of the electron stream upon the same single spot or line of the mosaic or fluorescent screen, thereby burning or otherwise damaging the mosaic or fluorescent screen.

In order to prevent this occurrence, it is necessary that the electron-stream current be reduced or cut off in the event of failure of the horizontal or vertical deflection voltages, or both. It has accordingly been proposed to feed components of the horizontal and vertical deflection voltages to a gating tube. An electro-mechanical relay or switch has been disposed in the output circuit of the gating tube to disconnect the electron gun of the cathoderay device from one of its sources of bias or operating potential in the event that the gating tube is rendered inoperative upon loss of either the horizontal or vertical deflection voltages, or both. While such devices have been found in many cases to work satisfactorily, they are subject to the principal disadvantage that the relay is an electro-mechanicaldevice, subject to the inherent unreliable properties of such devices.- The relay contacts may, forl'exaniple, become pitted, they may stick together, or other-electrical or mechanical defects may arise. In addition, circuits of the above-described character are expensive since theyinvolve utilizing the relay to switch very high electron-gun operating or bias voltages and require high-voltage rating precautions. The switching of such high voltages, moreover, further limits the period of faultfree operation of the relay and requires the utilization of specially designed relays. H

A n object of thep'resent invention, therefore, is to provide a new and improved electronic protective system 'thatQshall not be subject to the above-described disadvantagesjan d that, to the contrary, shall be direct-acting without the necessity for the utilization of an electromechanical relay or other switching device.

' A further object is to provide such a protective system suggested for protecting -fiice that shall be relatively inexpensive to manufacture. and that shall embody only a minimum number of standard electronic components for its operation.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawing, the single figure of which is a schematic circuit diagram illustrating the invention in preferred form.

An electronic cathode-ray apparatus of the electronbeam or electron-stream-producing type is shown at 1, provided with an electron gun comprising an electronemitting cathode electrode 3, a control-grid electrode 5, and an accelerating apertured anode electrode 7. The anode electrode 7-, the control-grid electrode 5 and the cathode electrode 3 are provided with operating and bias voltages for the electron gun. The anode electrode 7 is connected to a source of positive potential 9 and the control-grid electrode 5 is connected at 11 to an intermediate point of a bleeder resistor 12 the upper terminal of which is connected to a negative terminal and the lower terminal of which is grounded at 70. The cathode 3 is connectedthrough a resistor 13 to the ground terminal 71. The cathode 3, in response to operating voltages, is caused to emit electrons which are accelerated past the control-grid electrode 5 through the aperture 14 in the accelerating anode 7, finally to impinge upon a screen 15. The screen 15 is illustrated in the form of a conductive television-cameramosaic screen containing a light-sensitive mosaic 17 upon which any desired light image that is to be televised, may be projected. The electron stream is caused to scan the mosaic 17 along orthogonal horizontal and vertical directions by conventional horizontal deflecting means 19, and vertical deflecting means 21, fed, respectively, by conductors 23 and 25 with horizontal and vertical deflection voltages, as is well known. The deflection means 19 and 21 may be electromagnetic or electrostatic deflection means, as desired, and the cathode-ray apparatus lmay be provided with further electrodes, including focusing anodes, not shown for purposes of simplicity. In the event that the cathode-ray apparatus 1 is a television camera or pick-up tube, as before described, having a light-sensitive mosaic 17 mounted upon the conductive screen 15, the signal resulting from the scanning of the electron stream upon the light-sensitive mosaic 17 may be developed across the load resistor 29 and extracted by a conductor- 27.

While the present invention has thus far been described in connection with a television camera or pick-up tube 1, it is to be understood that thedescription and the use of the present invention are equally applicable to the case where the apparatus 1 constitutes a cathode-ray display apparatus having, for example, a transparent fluorescent viewing screen 15 comprising one or more phosphor layers, instead of the mosaic 17. In such event, of course, no output signal will be extracted, so that the elements 27 and 29 are not required, the viewer merely observing the fluorescence of the screen as the electron stream impinges thereupon. 7

In accordance with the present invention, a portion of the horizontal deflection voltage is applied tothe terminals 31, 33, the latter of which may be grounded, as at 35. A rectified component of the horizontal deflec tion voltage is obtained by passing the same through, for example, a diode rectifier 37, which may be ofthe electron-tube, crystal or solid type. There will thus be developed across the resistor 39 a positive rectified com ponent of the horizontal deflection voltage which may be applied by conductor 18, between, for example, the screen-grid electrode 41 and the cathode 43 of an electron tube 45, illustrated as of the pentod'e type. A portion of the vertical'deflectionvoltage may similarly be I 'It is preferable, accordingly, to

applied-toterminals 51 and 53 across the input resistor 55. The lower terminal ofi'the resistor 55 is preferably connected to a negative source of bias voltage, labelled --V E*, the' positiveterminal of which may be grounded, as at" 57. A rectifier 59; which may be similar to the rectifier 37, is shown-developing across a further resistor 61 21 positive-rectified component of the vertical deflection voltage.- This component maybe applied by conductor 63 to the control-grid electrode 47 of the electron tube 451 The-input circuit to the tube 45 thus comprises hoth 'the'connections 18 and 63 to the screen-grid electrode 41 andthe control-grid electrode'47 of the tube 45. The resistor 61, and the similar resistor-39ass0ciated With the horizontaldeflection voltage rectifier 37, are shownbypassed by respective condensers 77 and 79. The-suppressor electrode-4Q of-the electron tube 45 is connected-to -thecathode 43 by conductor 16.

In the above descri-bed circuit, unless the vertical de flection volt-ageds received at the terminals '51, 53, and itstpositive r-ect-i-fied component is developed by the rectifiefS-QE and applied to the control-gridelectrode 47 of the tube45, the control-grid electrode 47 will be'negatively biased,..by the before-mentioned source VE, with respectsttoithetcathode 43,-rendering'the tube 45 inefiective to-conduct. Assuming, however, that the rectified component ofi thevertical deflection voltage is applied to the;portion of xthe-input circuit ofthetube 45 comprisi ng;the\ connection 16310 the control-gridelectrode 47, the electron tube" 45' will conduct and-currentwill flow betweenits cathode 43 and plate:65:- This current, however, .wilbbe controlled by the potential applied to the screen-gridsuelect rode 41. Only if a positive rectified component of theihorizonta l deflection voltage is applied to thescreen-igri'd .electrode 41 by conductor 18, can an appreciable;predetermined current flow through the electron tube; 4510. the anode 65i In iordertthatsuclra predeterminedcurrent may flow through: the electron: tube-45, therefore',-it-is essential that" both'the; rectified components of the; horizontal and vertical deflectionzvoltages besimultaneou'slyapplied to thenin'putecircuit 'gridsz47 andl41' of: the-tube 45; In that event;..thez flows oft the predetermined "current in the output circuitaconductorzfl; connected toctheanode'65 of the tube 45,..will develop .a. predetermined potential at the P9i k69frelative. to the ground. terminal 71. That po tential will modify .the normal potential. of the cathode 3 Ofiuthfi; cathode-ray apparatus 1, rendering the cathode 3 sulfi ciently negative with respectto thecontrol-grid electrode 5,=t o;epcrmitx.the: passage. ofan electron stream in thodc iltayadcvice: 1: to...the. mosaic. 17." Should a t; either or both .of tthe horizontal and vertical deflfifit nnavoltagesl occur, or shoulduth'erebe afailurein h9-PI ;Q l9l iPnrf the rectified-icomponents thereof, or the deflecting means '19 and21 or the connections thereto'become faulty, however, the value of the current flowing; throughthe tube 45 will be markedly reduced from t esaid; predetermined value.-substantial1y to zero. 12h w i ll;,r;esult in, arisein potential atthe point 69,- as th tube- ,45 is rendered ineffective, thereby raising the ialofthe cathode 3'relative to that of the controll ect-rode,- 5 of the cathode ray apparatus 1. Such a rthe ipotentialyof thecathodeu3. willveifect the limiting of, and preferably substantiallygthe:cutting-0E of, the electgon, stream in the'device. 1 protecting thescreen 15 fromthe burnsior damage before-described. The connectipn; of the outputconductor 67 by a substantially-direct ole tgical connectioni73 to, the cathode3, moreover, prov desyag simple and; highly efiective protective. arrangement for the-cathod'e-ray device 1 that eliminates all n e s ity.-forelectromechanical relays or switching deapply to the connection point 69-, through a resistor 75; a potential ofpositive polarity .and of sufiicient value that, upon the reduction of the current flow through the electron tube 45 below the previously mentioned predetermined value of current, apositive bias potential will be applied to the cathode 3, sufiicient to modify or limit, and preferably to cut-ofi, the electron stream flow in the cathode-ray tube 1.

It is to be understood that, if desired, the protective control of the cathode-ray electron stream may beet: fected by rendering the control-grid electrode 5 neg tive with respect to the cathode 3, instead ofren'dering the cathode 3 positive with respect to the control-grid elec; trode 5. v This may be accomplished through reversal of the operating conditions of the tube 45, such that the tube fails to conduct only in the absence of either the hori! zontal or vertical deflection voltages. Not only may the control of the cathode-ray device 1 be effected at other electrodes thahthecathode-3; but-other typesoifelectron tubes besides the 'pentod'e '45'n1ay also be utilized a8 protective controlli-ng elements. In the case of tubes that can provide reliable cut-oft characteristics upon" of one or both of thedeflection voltages, the potential supplied through the resistor '75 may not be necessary:

Furthermod-i-fications will occur to those skilledin the artand all such are considered to fall within the spi v and scope-of theinvention, as defined in. the appended claimsr V V I I V What isclaimedis: V

1. An electricsystemhaving, in'combination;electronic apparatus provided with means for producing an electron stream: and; means for 1 deflecting the electron stream; electron-tube meanshaving input'and output circuits,-mea for applying to the input circuit rectifiedcomponents one or more elect'ron stre'am deflection voltages 'to-be-app'lied t'o. the deflecting means, the=reetifiedeomponen 7 having: such polarity as-to-permi-t-apredeterrnined curr to flowthrough the electron-tube mean-s into the-font circuit during the saidapplication of the 1 rectified cdni ponents,- and. an electrical connection from the output cit cuit to the electron-strearn-producing means for biasing the operation of the electromstreatn-prodncingmeans accordance with the potential developed in the output'cifi cuit ofitheelectron-tube means: :f

-2. An-electric systemhavi-ng; in combinati'qn,;-eleetronie. apparatus provided with means for producing an elect stream and means for deflecting the electro'n stream; el tron-tube means having'input' and output circuits, mean! for applyingto the input circuit rectified' fcomponents'of one or more electron-streamdeflection voltages tobe a" plied to the deflectingmean s,*- the" rectified componeni having such :polarity' a'sto permit apredetermined burr to flow-"through the electron-tube means "into the output circuit during-thesaid application ofthe rectified" ponents'; an electrical connection from the output circu to the electron-stream-producing means-for biasiiigthq operation of the electron-stream-producingfmeans-irr cordance with the potential-developed in the out'putcirc of the electron-tube means, and means for applying-- the said electrical 'connection a-potential of proper s' and-ofvalue sufiicient to modify theoperation of-tlieclog tron-stream producing means' only upon variation orange current 'fl'ow throughthe" electron-tube means -from-f said; predetermined current; I

3. An electric system having, in-combinatiomtelectrofi apparatus provided withgmeans for. producingclaw stream and means; for deflecting-the electronrstream, our tron-tube means'having input and-outppt; circuitsjtmem o a ply n 9 e nput rcu t fi d mpen n s one or'morel electron-stream deflection voltages-to be: plied 'to thedeflecting means, the, rectifiedcompo having s'uch polarityas to permit a predeterminedfcu flow. hr u he l onube m n n o t e circuit during" he" 11 ap ica iqnp he" s p ne n 'calrpnn iqn' i on! the ou to the electron-stream-producing means for biasingthe operation of the electron-stream-producing means in accordance with the potential developed in the output circuit of the electron-tube means, andmeans for applying to the said electrical connection a potential of proper sign and of value sufficient to limit the operation of the electronstream-producing means only upon a reduction in the current flow through the electron-tube means below the said predetermined current.

4. An electric system having, in combination, electronic apparatus provided with means including an electronemitting cathode electrode, an anode electrode and at least a control-grid electrode for producing an electron stream and means for deflecting the electron stream, electron-tube means having input and output circuits, means for applying to the input circuit rectified components of one or more electron-stream deflection voltages to be applied to the deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, and an electrical connection from the output circuit to one of the electron-stream-producing-means electrodes for biasing the operation of the electron-streamproducing means in accordance with the potential developed in the output circuit of the electron-tube means.

5. An electric system having, in combination, electronic apparatus provided with means including an electronemitting cathode electrode, an anode electrode and at least a control-grid electrode for producing an electron stream and means for deflecting the electron stream, electrontube means having input and output circuits, means for applying to the input circuit rectified components of one or more electron-stream deflection voltages to be applied to the deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, an electrical connection from the output circuit to one 'of the electron-stream-producing-means electrodes for biasing the operation of the electron-stream-producing means in accordance with the potential developed in the output circuit of the electron-tube means, and means for applying to the said electrical connection a potential of proper sign and of value suflicient to modify the operation of the electron-stream-producing means only upon variation of the current flow through the electron-tube means from the said predetermined current.

' 6. An electric system having, in combination, electronic apparatus provided with means including an electronemitting cathode electrode, an anode electrode and at least a control-grid electrode for producing an electron stream and means for deflecting the electron stream, electrontube means having input and output circuits, means for applying to the input circuit rectified components of one or more electron-stream deflection voltages to be applied to the deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, an electrical connection from the output circuit to one of the electron-stream-producing-means electrodes for biasing the operation of the electron-stream-pro-ducing means in accordance with the potential developed in the output circuit of the electron-tube means, and means for applying to the said electrical connection a potential of proper sign and of value suflicient to limit the operation of the electron-stream-producing means only upon a reduction in the current flow through the electron-tube means below the said predetermined current.

7. An electric system having, in combination, electronic apparatus provided with means for producing an electron stream and means for deflecting the electron stream along a pair of directions, electron-tube means having input and output circuits, means for applying to the input circuit rectified components of a pair of electron-stream deflection voltages to be applied to the pair of deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, and an electrical connection from the output circuit to the electron-stream-producing means for biasing the operation of the electron-stream-producing means in accordance with the potential developed in the output circuit of the electron-tubemeans.

8. An electric system having, in combination, electronic apparatus provided with means for producing an electron stream and means for deflecting the electron stream along a pair of directions, electron-tube means having input and output circuits, means for applying to the input circuit rectified components of a pair of electron-stream deflection voltages to be applied to the pair of deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, an electrical connection from the output circuit to the electron-stream-producing means for biasing the operation of the electron-stream-producing means in accordance with the potential developed in the output circuit of the electron-tube means, and means for applying to the said electrical connection a potential of proper sign and of value sufiicient to limit the operation of the electronstream-producing means only upon a reduction in the current flow through the electron-tube means below the said predetermined current.

9. An electric system having, in combination, a television pick-up tube provided with means including an electron-emitting cathode electrode, an anode electrode and at least a control-grid electrode for producing an electron stream and means for deflecting the electron stream along a pair of substantially orthogonal directions, electron-tube means having a plurality of electrodes including a plate, an input circuit connected with electrodes other than the plate, an output circuit connected with the plate, means for applying to the input circuit rectified components of a pair of electron-stream deflection voltages to be applied to the pair of deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron tube means into the output circuit during the said application of the rectified components, and an electrical connection from the output circuit to one of the electronstream-producing-means electrodes for biasing the operation of the electron-stream-producing means in accordance with the potential developed in the output circuit of the electron-tube means, the said potential developed during the flow of the predetermined current permitting the production of the electron stream.

10. An electric system having, in combination, a television pick-up tube provided with means including an electron-emitting cathode electrode, an anode electrode and at least a control-grid electrode for producing an electron stream and means for deflecting the electron stream along a pair of substantially orthogonal directions, electron-tube means having a plurality of electrodes including a plate, an input circuit connected with electrodes other than the plate, an output circuit connected with the plate, means for applying to the input circuit rectified components of a pair of electron-stream deflection voltages to be applied to the pair of deflecting means, the rectified components having such polarity as to permit a predetermined current to flow through the electron-tube means into the output circuit during the said application of the rectified components, an electrical connection from the output circuit to one of the electronstream-producing-means electrodes for biasing the operation of the electron-streram-producing means in accord 

